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Poplar Genome Sequenced and Published; Model Crop for Biofuels

Desired traits for the biofuels-optimized poplar. Click to enlarge. Source: DOE

A four-year scientific and technical effort has resulted in the sequencing and publication of the genome of the poplar tree. The effort, led by the US Department of Energy’s Joint Genome Institute (DOE JGI) and Oak Ridge National Laboratory (ORNL), united the efforts of 34 institutions from around the world, including the University of British Columbia, and Genome Canada; Umeå Plant Science Centre, Sweden; and Ghent University, Belgium.

A paper highlighting the analysis of this first complete DNA sequence of a tree is published in this week’s edition of the journal Science. The work on the Populus trichocarpa—black cottonwood—genome will support the development of trees as a ideal feedstock for a new generation of biofuels such as cellulosic ethanol.

Poplar’s extraordinarily rapid growth and its relatively compact genome size—480 million nucleotide units, 40 times smaller than the genome of pine—are among the many features that led researchers to target poplar as a model crop for biofuels production.

In the DOE-USDA Billion-Ton Study, corn stover and perennial crops such as switchgrass and hybrid poplar make up about half the potential 1.3 billion tons of annual biomass that could be available by the mid-21st Century. (Earlier post.)

(The Billion-Ton Study found that the United States has enough agricultural and forestry land to support production of more than one billion tons of biomass annually, which could provide enough liquid biofuels to replace more than a third of current transportation fuel consumption, and still continue to meet food, feed, and export demands.)

Under optimal conditions, poplars can add a dozen feet of growth each year and reach maturity in as few as four years, permitting selective breeding for large-scale sustainable plantation forestry. This rapid growth coupled with conversion of the lignocellulosic portion of the plant to ethanol has the potential to provide a renewable energy resource along with a reduction of greenhouse gases.

—Dr. Sam Foster, US Forest Service

Among the major discoveries yielded from the poplar project is the identification of more than 45,000 protein-coding genes, more than any other organism sequenced to date, approximately twice as many as present in the human genome (which has a genome six times larger than the poplar’s).

The research team identified 93 genes associated with the production of cellulose, hemicellulose and lignin, the building blocks of plant cell walls. The biopolymers cellulose and hemicellulose constitute the most abundant organic materials on earth, which by enzymatic action, can be broken down into sugars that in turn can be fermented into alcohol and distilled to yield fuel-quality ethanol and other liquid fuels.

Poplar is the most complex genome to be sequenced and assembled by a single public sequencing facility and only the third plant to date to have its genome completely sequenced and published.

In a research roadmap for cellulosic ethanol—Breaking the Biological Barriers to Cellulosic Ethanol: A Joint Research Agenda—released earlier this summer (earlier post), the DOE outlines some of the traits of a poplar optimized for biofuels.

Fundamentally, the goal is deliver faster-growing trees that produce more readily-convertible biomass. For example, genetic engineering has already been used to limit and alter lignification to maximize biomass-to-energy conversion. The resulting trees had normal growth and development, but the pulping time was reduced by more than 60%.

In an editorial in Science earlier in the year, Steven Koonin, Chief Scientist for BP, wrote:

Genetic improvement of energy crops such as switchgrass, poplar, and jatropha has barely begun. It will be important to increase the yield and environmental range of energy crops while reducing agricultural inputs. Plant development, chemical composition, tolerance of biotic and abiotic stresses, and nutrient requirements are important traits to be manipulated. The combination of modern breeding and transgenic techniques should result in achievements greater than those of the Green Revolution in food crops, and in far less time.

The poplar project supports a broader DOE drive to accelerate research into biofuels production. In August, the department announced it would spend $250 million over five years to establish and operate two new Bioenergy Research Centers. (Earlier post.) The DOE-supported research into biofuels is focusing on both plants and microbes, in an effort to discover new biotechnology-based methods of producing fuels from plant matter (biomass) cost-effectively.

Secretary of Energy Samuel W. Bodman has set a departmental goal of replacing 30% of current transportation fuel demand with biofuels by 2030.

Geographic distribution of potential biomass energy crops. Popular (outlined in yellow) can grow in most targeted regions of the country. Click to enlarge. Source: DOE.

Vast poplar farms in regions such as the Pacific Northwest, the upper Midwest, and portions of the southeastern U.S. could provide a steady supply of tree biomass rich in cellulose that can be transformed by specialized biorefineries into fuels like ethanol. Other regions of the country might specialize in different energy crops suited to their particular climate and soil conditions, including such plants as switchgrass and willow. In addition, a large quantity of biofuels might be produced from agricultural and forestry waste.

The DOE Joint Genome Institute, supported by the DOE Office of Science, unites the expertise of five national laboratories, Lawrence Berkeley, Lawrence Livermore, Los Alamos, Oak Ridge, and Pacific Northwest, along with the Stanford Human Genome Center to advance genomics in support of the DOE mission related to clean energy generation and environmental characterization and clean-up.

DOE JGI’s Walnut Creek, Calif. Production Genomics Facility provides integrated high-throughput sequencing and computational analysis that enable systems-based scientific approaches to these challenges.




We switched to coal to save the we are going to trees to prevent the CO2 from coal. How odd.


I have read that Brasil is getting excellent results from sugar cane for bio-fuels, is this crop too labor intensive to grow in NAmerica? Obviously the area in NAmer that has the proper temperature and rainfall requirements is limited, but it would seem a good option to keep on the table.


There aren't many areas in North America where it would be economically/environmentally feasible to grow sugar cane.

Sweet Sorghum, however, could be easily grown throughout the midwest of the United States and would produce roughly twice the ethanol yield of corn from lower inputs (water).

For all the money/energy we put into these projects (fuel from trees), why don't we just install friggin solar panels?


Poplar tress are nothing like a forest. They grow massively fast and are generaly cut down very often. Its far more like a farm then any other kind of wood. By geneticaly altering the tree they may actauly get a tree that grows to harvestable size in just 1-2 years.


Keep in mind that this is solar energy.


DOE's goal of 30 percent transportation demand as biofuel by 2030 (a quarter century away) seems overly conservative. These biofuels can be brought online sooner if the market and political will is there. If the goal is to transition to say 60-70 percent PHEV hardware over the same timeline, the biofuel sources should be well established and even diminish as better electric technology replaces the ICE. It is however, encouraging to see DOE acknowlegment biofuel as an immediate, transitional energy source. Finally we begin to use our sun and the energy it is endowed with.


IF someone tries to put a GM crop out in the open, depending on state, there will probably be a long drawn out legal battle. This is currently taking place in Washington over GM crops they want to setup strictly for research purposes on University owned property.


My concern with this project is that if these trees produce a wood that makes inferior lumber and it cross pollinates with non-GM poplars, it could trash the poplar lumbering industry. Or if they cross pollinate and a lot of poplars obtain the super fast growing genes, it could choke out the other tree species in forests.


Exactly the kind of sentiment brought forth in the litigation (I believe against WSU to prevent bio-fuel GM plant growth). You can't control the wind and pollen off the trees.


If it were legal to grow industrial hemp, no genetic modification is really needed (although I'm sure Monsanto, etc would disagree) for incredible biomass production. They can grow 8-20 feet in one season, and also produce oil and carbohydrates via seeds, but I suppose the failed(ing) war on drugs can't allow anything of the sort.

tom deplume

I saw silver maple listed as an energy crop. Here in Michigan they grow like weeds and are very resilient. There is one in my yard that is growing through a chain link fence which I cut off every year but keeps growing back in spite of my efforts.


Erick, then where is Canada's or the EU's massive bio-fuel production from the incredible biomass production value of hemp? Is it really that much greater than other crops and if so refer to the first question.?


I wouldn't worry too much about the poplar-lumbering industry, because I'm not aware that it exists. Poplar wood is soft and weak and not useful for much. The major use of poplar I see today is as a quick growing tree that builders put up in subdivisions. Unfortunately it is usually ugly and diseased or dead after 10 years or so.

Tom, I'm also in Michigan, and yes those silver maples are incredible weed trees. However I don't think they grow nearly as fast as hybrid poplars. I think silver maple was actually the subdivision builders fast-growing tree before hybrid poplars took over.

Bike Commuter Dude

Patrick: Hemp does provide benefits. But, it is also illegal to grow in most industrialized countries. This makes is very difficult to grow the large amounts needed to produce any amount of biofuel. So, if they legalize it at some point, that may produce industry growth. Furthermore, any amount that is being grown has a high value (low supply) for textiles, food additives, cleansers, etc. So currently it is too expensive for biofuels.

Patrick/TROy: These GM trees are designed to have floral sterility... The pollen and/or pistils of the tree's flowers are not able to combine. The plant version of antagonistic inhibition.


There is [a silver maple] in my yard that is growing through a chain link fence which I cut off every year but keeps growing back in spite of my efforts.

Check out the ancient practices of coppicing and pollarding.


Poplar wood may not be useful for much, but the spindly trees make excellent pulp. Driving through the columbia basin north of portland you will see miles of poplar plantations destined for the pulp mill. I'd imagine there is still a ways to go with selecting and hybridizing before we need to go GM to increase yields.


One of the desired properties listed in the graphic is floral sterility, which would prevent cross-polination. You want this so that it grows where you plant it (in neat rows?) and nowhere else, nor do you get young saplings growing next to mature trees, thus making it a crop that can be harvested all at once.


The poplar trees don't have to be GM. Breeding alone offers huge potential. Food crops have been bred for thousands of years (plant generations) and energy crops, such as trees, only for maybe five to ten generations.

Also GM trees couls also be sterile therby preventing pollen flow. Also they could be harvested before they are mature.


Ethanol production from sugarcane has being carried out for some decades already. It has become a profitable business and is no longer so labour intensive, new machines can easily harvest this crop.
Sugarcane is planted even in frost-hazardous regions, like my home state, for instance, although its area has diminished recently for many reasons, such as low sugar prices, higher uses for land and increase of productivity and production in other states of more suitable climate.


Genetic improvement of sugarcane moves in two oposite directions here in brazil. Since it is one of the best fodders for dairy and meat cattle selection is aimed at plants of low lignin content. But for the production of sugar/ethanol selection is aimed at plants of high lignin content, for the stem needs it to grow higher and enhance production.

Ron Lunnum

This has been a very informative article about different clones of poplar.One commentis that for the processing of alternative fuels by gasification a clone with maximum lignin would be preferred. This is because lignin is a very good raw material.
Perhaps the companies with lots of nasty lignin would like me to take it off their hands.

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